Using industrial lasers to treat surface material is known in the prior art. These treatments include glazing, sealing, marking, and drilling. Of particular relevance to this invention are a number of proposals to remove, by laser ablation, material from an underlying substrate. For example, United States patents have issued for removing paint, grease, dirt, rubber, ceramic, mineral scale, dielectric, and electrical conductor surface material by means of laser ablation. See:
U.S. Pat. No. Re. 33,777 issued to Woodroffe [paint, grease, ceramics] PA1 U.S. Pat. No. 5,592,879 issued to Waizmann [dirt] PA1 U.S. Pat. No. 5,637,245 issued to Shelton et al. [rubber] PA1 U.S. Pat. No. 5,113,802 issued to Le Blanc [mineral scale] PA1 U.S. Pat. No. 4,671,848 issued to Miller et al. [dielectric coating] PA1 U.S. Pat. No. 3,941,973 issued to Luck et al. [electric conductor]
Previously, removing surface material frequently required physical or chemical methods. These methods included physical abrasion, blasting surfaces with media such as sand, and using chemical solvents. Not only did these methods often damage the substrate, but the removal of surface material created a new problem; disposing of a waste stream bloated with contaminated cleaning material.
The potential commercial advantages of using laser ablation are significant. Not only is the waste stream to be treated and disposed of much reduced but there is potentially less recontamination of the surface itself. For example, chemicals used in the prior art to strip surface contaminates themselves could recontaminate the surface. Another advantage is that a beam of electromagnetic radiation may be fine-tuned to ablate surface material ranging from microfine contaminants to visible discrete particles. And, of course, the beam can navigate exceedingly narrow passageways as well as ablate material from microscopic pores.
However the problems inherent in creating a workable system have limited laser ablation technology to a few niche applications. These problems include high cost, non-transportable equipment, contamination of optics by ablated material, laser damage to internal optics, deficient feedback and control, inadequate safety systems, lack of ablation waste collection and containment, the need to isolate sensitive equipment from soily worksites, interference of ablation detritus with the beam at the work surface, and the difficulty of delivering a quality beam of electromagnetic radiation over distance.
A known way to deliver electromagnetic radiation is via fiber optics. However, a persistent problem has been the difficulty of inserting a high power laser beam into a fiber optic strand. Particularly, the entrance face of the strand is a barrier. A high power laser beam impinging upon the entrance face is analogous to a tsunami striking a sea wall. It turns out that in a fiber of a given diameter, the amount of energy that the fiber can transmit is about ten times the amount that can be inserted at the entrance face without damage to the face.